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5 The Land Acquisition Process and Biological Preserves: A Role for Natural Sciences This chapter examines several ecological issues that pose challenges to He acquisition of conservation lands and reviews Be current state of knowledge regarding Lose issues. The dynamic nature of landscapes and ecological systems is reviewed at multiple scales, as is the impor- tance of maintaining species and functional ecosystems in lands designat- ed for conservation and the role of spatial configuration in reserve de- sign. The effectiveness of the current set of criteria are evaluated for their effectiveness in addressing Me biological components of the agen- cies' explicit objectives and the issues noted above. Finally, the com- mittee's findings are synthesi ed and some modifications to He acquisi- lion process are suggested that could enhance the ability to meet the ecological component of acquisition goals. FUNDAMENTAL ECOLOGICAL CHALLENGES Geomorphic Processes Geomorphic processes are the physical and chemical processes that determine the distribution of energy within a changing landscape. The distribution of moisture, nutrients, temperature, sediments, and other resources on ache landscape affect and are integral to He biological re- sources, productivity, and diversity of ecosystems. Conservation of ~3
A ROLE FOR NATURAL SCIENCES 115 diversity, a management objective should be to maintain adequate habi- tats for populations over a wide geographical area. This is particularly important for adapting to rapid environmental change. Species Diversity Technically, species richness refers to the number of species present; species diversity is a measure of the number of species and their relative abundance. With habitat fragmentation and disturbance, species become increasingly rare. Data must be acquired on minimum viable population sizes and sizes of habitats required to sustain them. For example, Samp- son (1980) estimates that populations of the greater prairie chicken can be sustained only on grasslands of 300 hectares or larger and that they also must be within 20 km of other undisturbed grasslands. Community Diversity This concept generally refers to the number of= species inhabiting an area and encompasses all trophic and nontrophic interactions. Many of these interactions are highly species-specific. For example, many spe- cies of herbivorous insects depend on specific plant species. Whitcomb (1987) reports that assemblages of leaflloppers in grasslands were depen- dent on the patch size and structure of host stands, and the rarity of these insects was attributable to the rarity of Weir host plants. Popula- tions such as these in small, isolated patches are particularly sensitive to disturbance by physical (e.g., fired and biological forces (e.g., parasites, predators). GIobal-&ale Diversity Conservation of diversity must also be considered at a global scale for species with migratory habits (e.g., marine mammals and birds). Also, biogeochemical cycles can be influenced strongly by global phenomena' such as decreasing ozone. Decisions to acquire land for conservation should be based upon a
A ROLE FOR NATURAL SCIENCES 117 The factors controlling species distributions differ with scale. For example, in He Southwest, He mortality of oak seedlings at local scales decreases with increasing precipitation, whereas moronity at regional scales is lowest at the drier latitudes (Neilson and WulIstein, 1983~. In an area of the Laurentian Great Lakes in Ontario, regional patterns of fish assemblages appear to be determined by postglacial dispersal and lake Herman regimes, whereas environmental conditions such as lake depth and pH assume greater importance in determining species compo- sitions of individual lakes (Jackson and Harvey, 1989~. Finally, a dynamic landscape in which the proportions of different habitat types change through time might exhibit a stable mosaic (Bor- mann and Likens, 1991) at one spatial or temporal scale but not at an- o~er. Without a temporally stable patch mosaic at any spatial scale, fluctuation and change might predominate within areas of any sue (Bak- er, 1989a). These examples suggest that the importance of spatial and temporal scale as they influence conservation objectives must be considered in the planning for land acquisition. Within a single locality or preserved area, emphasis may be placed on preventing the local extirpation of a species or maintaining a representative habitat type. A particular parcel of land may also be valuM for its aesthetic or recreational value. Therefore, conservation goals at the local level may emphasize the perpetuation of a particular ecosystem type. Manipulative management might be re- quired to preserve populations within a local area, but that might conflict with attempts to ensure the perpetuation of broad-scale processes (Baker, 1989a). The landscape level a mixture of natural and human-managed patches that vary in size, shape, and arrangement (Burgess and Sharpe, 1981; Forman and Godron, 1986; Urban et al., 1987; Turner, 1989~. Conser- vation goals may focus on maintaining a particular juxtaposition of habitat patches. The size and geographic arrangement of patches across a landscape may influence species success or persistence, and many wildlife species are wide-ranging and make use of several habitats (For- man and Godron, 1986~. Management or conservation goals might be to perpetuate natural fluctuations in landscape structure (e.g., a natural fire regimes, which implies Hat certain species may fluctuate as well. If long-term maintenance of biological diversity is a conservation goal, a management strategy that places regional biogeography and
118 SETTING PRIORITIES FOR LAND CONSERVATION landscape patterns above local concerns may be necessary (Noss, 1983). The acquisition of conservation lands would then require an evaluation not only of the habitat within a protected area but also the landscape context in which each preserve exists (Noss and Harris, 1986~. When assessing the effectiveness of the criteria by which conservation lands are acquired, the appropriate objectives at multiple scales must be con- sidered. Landscape Dynamics Land conservation is challenging in part because one goal is to pre- serve areas that are changing (White and Bratton, 1980~. When consid- ered over long periods, Me species assemblages observed today are relatively recent (Delcourt and Delcourt, 1991~. Many have formed only in the past 10,000 years and reflect individual species' responses to changes in the global environment. Over shorter periods decades to centuries the patterns of many landscapes are influenced by natural disturbances (White, 1979; Mooney and Godron, 1983; Pickett and White, 1985; Turner, 1987; Baker, 1989b). Disturbances may create openings within forested landscapes, leading to patches of different ages (Runkle, 1985; Knight, 1987; Baker, 1989a,b). Landscape patterns in old-growth forests of New England, for example, result from frequent natural disturbances, such as windstorms, lightning, pathogens, and fire (Foster, 1988~. A variety of authors have suggested that natural areas should be sufficiently large to include all normal stages in community development, and that natural processes of perturbation and recovery should tee allowed to occur unchecked (Sullivan end Chaffer, 1975; Pickett and Thompson, 1978~. Even in the absence of natural disturbances, landscapes are not static. In the Southeast, for example, forested land has increased during the past 50-75 years after the wide-scale abandonment of marginal agricul- tural lands (Odum and Turner, 1990; Turner, 19901. In over areas, especially the Midwest, forest cover has declined Jverson, 1988; Dunn et al., 1991~. In addition, many land-management activities (e.g., for- estry practices, regional planning, and natural-resource development) involve decisions that alter landscape patterns, with important implica- tions for conservation (Franldin and Forman, 1987~. Thus, planning for conservation lands must always assume that the environment is dynamic.
A ROLE FOR NATURAL SCIENCES 12 components and processes of the area; an expectation of how these controls may change, either through natural events or human actions; and an evaluation of the probable effects of these changes on the ecolog- ical processes and biota of a region (Golley, 1984~. Disturbance regimes. The frequency, duration, and severity of abiotic and biotic disturbances are likely to be altered by climate change. For example, forest-fire frequencies should increase where the climate becomes warmer and drier (Sandenburgh et al., 1987~. Patterns of biotic disturbances might be altered. Because their ranges are often limited by climatic factors, the distributions of pests or pathogens might change win climate. Short-term climatic fluctuations provide important insights into the response times of species and landscape mosaics to rapid environmental changes in disturbance regimes on the order of decades to centuries. For example, in northwestern Minnesota, changes in the charcoal influx to lake sediments demonstrate how alternating periods of cool-and-moist cycles and warm-and~ry cycles since 1240 A.D. have influenced the periodicity of fire (Clark, 1988~. If ecological disturbance regimes are altered, changes are likely in many landscapes. Habitat types might be eliminated locally from certain areas. Thus, conservation planning must consider whether the size of an existing or proposed reserve in a disturbance-prone environment would be adequate to incorporate an alteration in disturbance frequency or severity. In addition, if an altered disturbance regime could lead to the loss of some habitats, the regional context of the reserve and We poten- tial for Me persistence of He desired habitat in over geographic loca- tions should be evaluated. Changes in the lo cation of suitable habitat. A second effect of cli- mate change might be a gradual movement of potentially suitable condi- tions for different species. Species would be expected to migrate to hospitable environments. However, migration rates are difficult to predict, because He rates of climate change are not predictable. Fur- thermore, Here are now new barriers to migration (e.g., cities, agricul- ture, and roads) and new modes of migration (e.g., cars, trains, trans- plants for horticulture, forestry, or agriculture.) Range extension In He future may be less efficient Han in the past, because advance disjunct colonies have been extirpated by human disturbances, and propagule sources often have been reduced (Davis, 1989a). The current spatial
A ROLE FOR NATURAL SCIENCES 123 parks. Current analyses of data on birds, butterflies, and small mam- mals from the Minimum Critical Sue of Ecosystems project suggest the importance of large areas ~ovejoy et al., 19861. Nonetheless, large and small are relative terms. A different approach is to examine the popula- tion of the lowest density species Frizzy bears or gray wolves in Yel- lowstone, for examples and determine the area necessary to support what could be considered a minimum viable population. This suggests that maximizing resewe size is desirable for maintaining species richness. It must be recognized, however, Nat even the largest nature reserves, if left alone, will probably suffer major die-offs of species in a few hun- dred or a few thousand years (Franke! and Soule, 1981~. For example, the huge Kruger National Park in Soup Africa about 350 km long and 80 km wide in places- requires significant management to protect many of its species from major population declines and perhaps even extinc- tions (Aiken, 1988~. Even if a habitat fragment is suitable to support a population of inter- est, there is no assurance Nat We population will remain viable if it is isolated from over populations, because genetic variability may be lost through inbreeding. The shape of a reserve and "edge effects" influenc- es the relative amount of edge to interior, which in turn influences bio- logical diversity and susceptibility to disturbance (Burgess and Sharpe, 1981; Ranney et al., 1981; Harris, 1984, Lovejoy et al., 1986~. A circular area, for example, has the lowest edge to area ratio, whereas a long, thin rectangle has a much larger edge to area ratio in fact, it may be all edge. For decades, the interspersion of habitat types, the creation of edge effects, and the juxtaposition of different kinds of plant communities were believed to enhance wildlife habitat values (Harris and Scheck, 1991~. It is now recognized that tile creation of distinct edges (e.g., clear-cuts next to old grouchy may reduce He biological value of an area by increasing susceptibility of undesirable disturbances (Franklin and Forman, 1987~. The effects of habitat fragmentation and connectivity have been stud- ied extensively through empirical studies and models. Miine et al. (1989) found Hat wintering white-tailed deer did not use sites containing suitable habitat Hat were isolated from other suitable sites. In northern Florida, approximately half of He breeding bird species characteristic of hardwood forests do not reproduce in small forest fragments occurring
124 SE7-llNG PRIORIDES FOR LAND CONSERVATION in an agricultural matrix (Harris and Wallace, 1984). In examining the effects of alternative arrangements of corridors of "equal strength" in a simulation model, Le~ovitch and Fahrig (1985) demonstrated that popu- lations In isolated patches experienced earlier local extinction and had tower average population sizes Wan patches connected by corridors to other patches. In addition, patches that formed part of a square or pentagon had higher population sizes and probability for survival Man those that formed part of a line or triangle. These results suggest that corridors or links between habitat patches can be a major factor in Me long-term survival of a population; however, such linkages may also enhance the spread of a pest species. It is generally accepted that the destruction and fragmentation of habi- tat is the most important cause of species loss. Landscape designs that facilitate movement and dispersal of native biota are preferred by conser- vationists over designs that do not (Soule et al., 1988~. Moreover, because there is already an established system of protected areas, the function of existing conservation lands would be enhanced by conser- vation strategies that emphasize movement and dispersal. While corri- dors may be beneficial to species and be critically important in mitigat- ing the effects of climate change, He role of corridors as an aid to dis- persal will vary by species. However, the presence of corridors should not be used to justify the establishment of smaller reserves (Franke! and Soule, 1981~. There are some examples of land acquisition to link protected areas across He landscape. According to Harris and Scheck (1991), 80% of Florida's largest protected natural areas are too small to contain a single pair of wide-ranging species, such as the Florida panther or black bear, and about 60% of the largest 315 areas are less than 400 hectares. The state of Florida, in conjunction with The Nature Conservancy, is in the process of acquiring land to link existing protected areas. Acquisition of the Pinhook Swamp on the Florida-Georgia border creates a federally owned protected area of 225,000 hectares that extends nearly 100 km (see Figure 5-~. Another project in Florida aims to consolidate several state and federal parks and protected areas along the Wekiva River norm of OrIar~do. This area will span more Han 150 km through He Ocala National Forest and along He Oklawaha River (see Figure 5-21. In He Southwest, U$FWS, He Texas Parks and Wildlife Deparunent, and several nongovernmental agencies are cooperating to develop He Rio
128 SEl-llNG PRIORIES FOR LAND CONSERVATION simple question if it is a fairly distinct, cleancut feature, such as a bog. The delimitation of bog vegetation is easily dete~ined. If, however, the objective is to protect a representative sample of biological commu- nity that is widespread, the question of size immediately arises. Wherever possible, habitat chosen for acquisition should not be frag- mented. Rather, habitat should be continuous but appropriately should include natural disturbance regimes. When it is not possible to find an area of continuous habitat Hat is large enough, two solutions are evi- dent: acquire the necessary area and encourage the return of natural vegetation between the fragments, or ensure the core area is surrounded by a matrix of habitat fragments and corridors that provide for species populations larger Can the actual protected area can. The best-chosen and best~esigned area for biological diversity con- servation is nonetheless vulnerable to outside factors. Total watersheds and their management need to be taken into account in design and man- agement. Otherwise problems may result, such as Be toxic agricultural runoff Hat poisoned waterfowl in the Kesterson Wildlife Refuge. Acid rain emanating from anthropogenic sources far from a resews can alter lake acidity and even growing patterns or survival of trees. While He extent, rate, and details of climate change introduced by artificial release of greenhouse gases might be a matter of disagreement, it could have a major negative effect on biological diversity (Peters and Lovejoy, 1992~. Few measures can be taken to avert such adverse effects. When possible, the best measure is to conserve attitudinal gradi- ents that will allow species to move upsIope in the event of temperature increase. If attitudinal gradients are not available, latitudinal gradients can be considered, but this involves much more extensive expanses of natural habitat. This assumes of course that the only climatic change will involve temperature as opposed to rainfall, snowmelt, directions of currents, etc. ENHANCING THE ECOLOGICAL EFFECTIVENESS OF THE ACQUISITION PROCESS Gap Analysis Past land-acquisition strategies have focused on saving critically en
A ROLE FOR NATURAL SCIENCES 131 \ ~ ~ ~~ Hualalai Kona \ Mauna Loa at' ~ \ n ~ A . Arch it -f ~ V''-1 / ~ / Naalehu FIGURE 5-3 Gap analysis of Hawaii. Source: Scott, 1991. Mauna Kea;\~ 1 Species 2 species O 3 species G 4 species id] Preserves years to complete. It is not clear whether gap analysis could be applied to aquatic systems. Geographic Information Systems The geographic information system (GIS) is a powerful tool to plan for and acquire lands. The power of GIS lies in the ability to manipu- late and analyze spatially distributed data (Figure 5~. A GIS consists of the computer hardware and software for entering, storing, transform- ing, measuring, combining, retrieving, and displaying digitized thematic
! A ROLE FOR NATURAL SCIENCES 133 data that have been registered to a common coordinate system. Because the data can be accessed, transformed, and manipulated interactively, they can serve as a testing ground for studying environmental processes, analyzing the results of trends, or anticipating the possible results of planning decisions 03urrough, 1986~. Planners and decision makers can use GIS to explore a range of possible scenarios (e.g., alternative ar- rangements of conservation areas) and evaluate potential consequences of a course of action before changes are made in the landscape. Impor- tantly, quantitative assessments can be conducted over a broad range of spatial and temporal scales. GIS is used widely in urban and regional planning, natural resource planning and management, and landscape architecture (Iohnston, 1987; Ripple, 1987; Johnson, 1990~. Forest managers routinely use Me inven- tory capabilities of GIS at the federal level (Chambers, 1986), state level (losta and Davis, 1987), and local level (Wakely, 19871. GIS also is being used to explore the implications of land-management alternatives. Application of GIS to aquatic conservation efforts is more difficult, although it has been used, for example, to establish buffer zones around rivers to determine how land use would change water quality Johnston et al., 1988; Osborne and Wiley, 1988~. GIS systems are easily linked with remote sensing imagery, and linkages with simulation models are being developed rapidly (CouIson et al., 1991~. A recent review of GIS applications in natural resources and ecology (Johnson, 1990) highlights several important operations that are relevant to conservation planning. First, GIS can be used to determine the spa- tial coincidence of different types of spatially distributed data. Coinci- dence analyses result in digital maps showing the areas of overlap be- tween two or more data layers (e.g., soils and vegetation). For exam- ple, GIS and remote sensing imagery have been linked successfully to predict the occurrence of species populations based on the coincidence of required habitat and environmental factors (Scepan et al., 1987; Sten- back et al., 1987; Hodgson et al., 1987) and to identify potentially suitable sites (Palmeirim, 1988; MiIne et al., 1989~. By selectively weighting habitat characteristics and describing spatial variables such as patch size, shape, and arrangement, die quality and quantity of habitat can be estimated Johnson, 1990~. Second, temporal changes in land- scape patterns can be quantified using GIS Person, 1988; Turner, 1990~. Although temporal analyses have emphasized the detection of
136 SEWING PRIORITIES FOR LAND CONSERVATION management agencies) accomplish their objectives In a variety of ways, ranging from day-to~ay management decisions at individual sites to agencywide decisions, such as assigning priorities for acquiring lands for conservation purposes. Each agency has a unique combination of mis- sions, traditions, policies, and explicit priorities Hat drive its land-acqui- sition policies. In principle, that diversity facilitates a variety of conser- vation strategies ranging from total protection of pristine lands to the acquisition of lands for intensive management and manipulation for specific objectives. But a critical question is whether this system gives adequate consideration to conservation issues that transcend the jurisdic- tiona] boundaries of the federal land-management agencies. Many additional important conservation issues are becoming apparent to the scientific community. A few examples are climatic change, de- clines in populations for entire groups of species, and fragmentation and ~nsular~zation of biotic communities. Natural ecosystems are spatially and temporally dynamic; furthermore, the importance of a single site to regional biological diversity is variable. The tendency, however, has been to establish geographically fixed wildlife refuges with immovable borders that inhibit species survival. Rivers are the products of their drainage basins, and We biological integrity of stream and river systems is dependent to a large extent on land uses and management practices in the entire watershed. Such land uses, as well as outside factors, such as demographics, must be consid- ered to identify and protect critical areas. Long-term planning is needed to develop a land-acquisition strategy that considers acquisition projects in the context of Be landscape on a scale appropriate to the needs of affected plant and animal species. A recent Naitonal Research Council report on restoration of aquatic ecosystems also addresses landscape considerations and suggests Rat {ong-term planning be done by regional planning programs organized by watershed basin (NRC, 1992b). The ultimate goal of conservation activities should be sustainability of renewable resources, Including cultural and biological dimensions. Addressing the problem of sustainability requires an interdisciplinary, complementary approach among natural and social scientists, as well as cooperation among agency programs with diverse and often conflicting mandates. Land-acquisition programs can play a significant role in achieving Be goal of sustainability Trough the acquisition of critical areas. Achieving sustainability requires a recognition of practices that are
138 SElTING PRIORITIES FOR LAND CONSERVA17ON dinate federal land acquisition, promote and facilitate collection and transfer of information, and develop a long-term plan aIld strategy for land acquisition. Such cooperation is a challenge that will require ~nsti- tutional innovation.
